To decrease a dependence of a color tone of a liquid crystal display device on an angle, a retardation film which meets a relation of 0.92≦R40/Re≦1.08, wherein Re is a retardation value at an incident angle of 0 degree and R40 is a retardation value at an incident angle of 40 degrees, or a retardation film which meets a relation of nx>nz>ny, wherein nx is a refractive index in a direction of a slow axis in a plane of the film, ny is a refractive index in a direction perpendicular to the direction of the slow axis in the plane, nz is a refractive index in a thickness direction has been proposed.
For example, Patent Document 1 discloses that a first anisotropic film is obtained by uniaxially stretching a polycarbonate resin film, a second anisotropic film is obtained by uniaxially stretching a polystyrene resin film on the other hand, and then the first anisotropic film and the second anisotropic film are overlapped so that directions of stretching of the films are at right angles to each other to obtain a retardation film which meets a relation of nx>nz>ny.
Moreover, Patent Document 2 discloses that a first anisotropic film is obtained by uniaxially stretching a polycarbonate resin film, a second anisotropic film is obtained by uniaxially stretching a polystyrene resin film on the other hand, and then the first anisotropic film and the second anisotropic film are overlapped so that directions of stretching of the films are at right angles to each other to obtain a retardation film which meets a relation of (Re—Re40)/Re≦0.07.
Patent Document 3 discloses that a laminate is formed by bonding a shrinkable film to one side or both sides of a resin film before the resin film is stretched, and then the laminate is stretched and heated to apply contractive force to the laminate in a direction orthogonal to the direction of stretching of the above-mentioned resin film to obtain a retardation film which meets a relation of 0<(nx−nz)/(nx−ny)<1.
Patent Document 4 discloses that a rod is obtained by extrusion of a melted polycarbonate resin, a disc is obtained by slicing up the rod in round, a rectangular plate is obtained by cutting the disc, and a retardation film which meets a relation of 0.92≦Re40/Re≦1.08 is obtained by uniaxially stretching the rectangular plate.    [Patent Document 1] JP-A-H03-24502    [Patent Document 2] JP-A-HO3-141303    [Patent Document 3] JP-A-HOS-157911    [Patent Document 4] JP-A-H02-160204